Desert Southwest Warming Faster Than Planetary Average

While the rest of the world has experienced a relatively moderate increase in temperature over the past five years, the American Southwest has begun to broil.

The National Resources Defense Council and the Rocky Mountain Climate Organization, both environmental-action groups, analyzed federal weather data from 2003 to 2007.

Their research, released Thursday, showed that although the globe warmed by an average of 1 degree Fahrenheit during that period, the West warmed by 1.7 degrees and Arizona by 2.2 degrees.

The temperatures were compared with the historical average of the 20th century.

The report, “Hotter and Drier: The West’s Changed Climate,” did not definitively pin the warming on the actions of people but said it is “very likely that most of the warming since the middle of the 20th century is the result of human pollutants.”

The National Resources Defense Council warned that the increase has already begun to affect the region’s agricultural, recreation and tourism industries.

Tony Haffer of the National Weather Service in Phoenix said there is no doubt the region has gotten warmer in the past five years. Haffer said, however, that it is still not clear whether the higher temperatures are the product of global warming or if this is just a normal, cyclical event.

“We’re in a drought cycle. When it’s dry, it’s warmer,” he said. “There is no question it is warmer. But what it means, that’s still a question.”

This new research folds neatly, perhaps ominously, into two other significant climate-change reports released in 2007.
Last April, the journal Science published a study that said rising temperatures will fuel longer and more intense droughts across Arizona and the Southwest. It warned of conditions not seen since the 1930s Dust Bowl.

What set that report apart from others was its assertion that changes had already begun.

There was also a broader assessment of global warming by teams of international scientists. That report charted a litany of ecologic and economic threats posed by man-made greenhouse gases and concluded that, in many areas, the threats were already real.